Building unit and construction



Jan. 3, 1939. c, F DAWS I 2,142,305

BUILDING UNIT AND CONSTRUCTION Original Filed Sept. 13, 19:52 9 Sheets-Sheet 1.

" INVENTOR p kmwrz/T'ww/i, BY I A TTORNEY 0 C. F. DAVIS I BUILDING UNIT AND CONSTRUCTION Jan. 3, 1939.

Original Filed Sept. '13, 1952 9 Sheets-Sheet 2 I N VEN TOR A TTORNE Y Jan. 3, 1939. c. F. DAVIS I I BUILDING UNIT AND CONSTRUCTION Original Filed Sept. 13, 1932 9 Sheets-Sheet 5 I N V EN TOR. C24/P/KF/T fiflV/J A TTORNE Y.

Jan. 3, 1939. v c, VI 2,142,305

BUILDING UNIT ANDCONSTRUCTION I Original Filed Sept. 13, 1932 9 Sheets-Sheet 4 p l I INVENTOH I ,4 CHI/ga f? fiflV/J,

' I ATTORNEY Jail. F, DAjVlS 2,142,305 I I BUILDING UNIT AVN-D CONSTRUCTION I Original' 'Filed Sept. 15 1932, 9 Shets-Shet 5 c. F. DAVl$ BUILDING UNIT AND CONSTRUCTIQ N- ori nal Filed Sept. 15, 1952 9 Sheeis-Sheet e, v

Jan. 3, 1939. c, F DAVIS 2,142,305

BUILDING UNIT AND CONSTRUCTION Original Filedsept. 13, 1932 9 Sheets-Sheet 7 ATTORNEY.

Jan. 3, 1939. v c, F, DAVls 2,142,305

BUILDING UNIT AND CONSTRUCTION Original Fil'ed Sept. 15, 1952 9 Shets-Sheet s INVENTOR. 62/42/127. fifly/a mwwwv A ATTORNEY.

Jan. 3, 1939. c. F. DAVIS BUILDING UNIT AND CONSTRUCTION Original Filed Sept. 13, 1932 9 Sheets-Sheet 9 ATTORNEY.

Patented Jan. 3, 1939 Clarke r. Davis, Short Hills, N. 1., assignor,

mesne assignments, to American Gyanamid by a:

Chemical Corporation, a corporation of Delaware Application September 13, 1932, Serial No. 632,909 Renewed February 23, 1938 12Claims.

The present invention relates to a building unit of set cementitious' material having on at least one of its edge portions a metallic element adapted to engage or be attached to a corresponding or complementary edge member on an adjacent unit. In my Patent 1,854,396, issued April 19, 1932,

I have shown and described one specific form of the invention, which consists of a building unit having a set cementitious body as of gypsum or the like, with .or without fillers, and having applied to an edge portion thereofa metallic element adapted to engage and interlock with a corresponding or complementary edge member on an adjacent unit as by a tongued and grooved joint.

Building constructions of today include many types of materials for floor and roof decks, partitions, walls, ceilings and the like, but as far as I am aware no type of construction has been designed which can equal wood in cheapness oi initial cost, flexibility of application and ease of erection. The use of wood, however, in many situations is objectionable from various standpoints, the principal one being that it is readi y combustible and involves, therefore, a fire hazard which makes its use prohibitive in many circumstances. Another objectionable feature of wood is that unit for unit it does not have the structural strength of metal and as a result if requisite strength is to be secured, such elements ii. of wood must be of such size and weight as to be prohibitive in cost and diflicult to handle, which oi course adds materially to the cost of erection. Moreover wood is subject to deterioration. All of the above necessarily classifies wood as an undesirable building material when viewed from these aspects, although it does have many desirable characteristics, as above outlined. a

The principal object of this invention, therefore, is to design a building unit which may be handled in the same manner as wood lumber or beams, which is fireproof or semi-fireproof, which is not subject to deterioration, and which through properly designed units may be made to sustain loads and stresses far greater than anything possible with a wood construction of the same dimenslons.

Other advantages and objects will be apparent as the description proceeds.

To this end the invention contemplates what may be termed a precast slab having a body of set cementitious material having a metallic mem her or members attached to or embedded in one or more edges thereof to either partly or fully enclose said edge or edges, the metallic element or elements, or other edge members being adapted to engage or interlock with a corresponding or complementary edge member on an adjacent slab.

It is contemplated by this invention that either the greater part or the whole of the load which this unit is capable of sustaining, will be borne 5 by the edge member rather than the cementitious body.

It is extremely difllcult to define all the forms this edge member may assume, for there are literally hundreds of diiierent constructions 10 which may be used to accomplish the above object. While some shapes are more efllcient than others, yet each may have its specific use to which it is peculiarly adapted rather than another. Perhaps the shape of most universal 15 use is substantially that shown in my prior Patent 1,854,396.

In view 01' the above dimculty it can only be said at this time that the invention contemplates with aprecast body any and all types of compara- 20 tively still edge members where those edge members are capable of sustaining loads greater than would be possible if the edge member were omitted from the cementitious body. It is preferable, of course, that there be some kind of interlock 5 between contiguous units to increase the load sustaining ability of the units and produce rigidity. This interlock may take the form of. continuous or interrupted tongues and grooves and positive interlocks as by splines having ,en- 30 larged ends, separate and integral keys, dowels, deformable tongues, splines or dowels, hinged or pivoted locking elements on one unit engaging projections or apertures in a contiguous element, projections on one element of the dovetail shape 5 adapted to engage a correspondinggroove on a contiguous element, making necessary longitudinally sliding one element into engagement with the other, shiplaps with or without a corresponding lateral interlock, poured in place keys 49 or splines 01 the same type of cementitious material of which the body is made, or of a stronger character such as concrete, artificial resins, metal or in fact any material which may be poured as a liquid or worked as a plastic and which will eventually set up into a comparatively stifi solid. The invention further contemplates the use of separate clamping elements not an integral part of the element or elements engaged thereby. The wide variety of forms thus enumerated will serve so to illustrate the difflculty experienced in definitely. defining such elements as a physical shape.

In use, units as above set forth may be made in any dimension with the metal or other edge member 01 any desired weight or thickness, the u design of which, however," will be determined by the particular problem in hand. Buch units may be used as sustaining or partition walls, roofs, ceilings, ornamental surfaces or in fact any situation where wood may be used, and many situations where wood could not be used.

If found desirable the metallic or strengthening edge member may exist on all four edges in order to give strength in two directions or may be only used on opposite edges or on one edge where the other edge is not designed to sustain a load. Such units may have necessary reinforcements therein where it is found desirable to have the main body thereof of sufficient strength to carry a portion of the load. This reinforcement may consist of rods,'mesh, structural shapes and in fact any type of internal construction which will lend load sustaining strength to an otherwise weak body not capable of sustaining a definite load without such reinforcement.

As designed, the weight or gauge of the edge members necessary to sustain all normal loads which might be experienced in building constructions will be found to be light enough to be sawed by a saw of the ordinary hack type. This lends flexibility to the application of the units as they may be sawed to fit any particular location or circumstance.

Due to the fact that the principal load sustaining attribute of these units can be traced directly back to the edge member and is not dependent to any great extent, if at all, to the cementitious body, the distance between centers of supporting members such as beams, girders, purlins or the like, whether of the I beam type, channels, bar joists, wood framing or whatnot, can be calculated not from the standpoint of the load sustaining value of the cementitious body, but on the contrary from the load sustaining value oi the engaged or interlocked metal members.

As set forth in my prior patent, I have found that under such circumstances the ratio of supporting element spacing to slab thickness need not be less than 24:1. When it will be remembered that in ordinary wood construction this ratio cannot be greater than 18 or 20:1, but on the contrary is usually from 12 to 15:1, the advantage of such a construction will be apparent.

Where gypsum either neat or with an admixture of fiber such as vegetable fiber of which wood chips is typical, or even with mineral fibers such as asbestos or the like is used, the ratio of support spacing to slab thickness is even less than that with wood. This means in an unedged gypsum slab, if a spacing 15 or 18 times the thickness of the slab is to be used, the slab thickness must be such as to make the slab expensive to manufacture both from the standpoint of cost of initial material and necessary reinforcement, and extremely difilcult to handle due to the excessive weight.

Slabs constructed according to the present invention are substantially fireproof and have high insulating value both as to heat and sound. In some forms the metallic edge members or a portion thereof, may extend over the face of the slab body or they may be embedded therein and not exposed. The latter is preferable from the standpoint of greater fireproofing qualities be cause in such instances the metal itself is not exposed to the heat of the fire, but on the contrary the intervening thickness of gypsum or other cementitious material serves to protect the metal from the ravages thereof.

The unit constructed according to the present invention forms an ideal surface for interior or exterior decoration, as it will make a strong 1 bond with any of the accepted plasters such as lime, gypsum or magnesium oxychloride or oxysulphate cements, plastic paints, oil or cold water paints and paper or cloth decorated surfaces applied thereto either by means of paint-like substances, size or glue.

Gypsum itself, which is an ideal material for the body, will not ordinarily hold nails permanently without loosening, and if such nails are driven near the unprotected edges, the gypsum has a tendency to crack or spall. This tendency, however, is materially decreased where a fibrous filler such as wood chips or the like is used. With the units of this invention, however, where the edges contain a strengthening or protecting element, when the nails are driven through this protecting element, and the invention contemplates in all cases that such material shall be of a gauge sufiicient to permit driving of nails therethrough, it is practically impossible to loosen such nails, due to the fact that the nail is not only gripped by the cementitious body, but is gripped by the metal or protecting element through which the nail penetrates, and this metal or protecting element co-operates with the gypsum body to prevent any loosening eflect which may later occur due to the fact that the nail is held rigidly in this desired position and against lateral movement.

The invention further consists in the novel arrangement, combination and construction of parts hereinafter more fully described and shown in the accompanying drawings.

In the drawings Fig. 1 is a fragmentary perspective view of contiguous slabs showing a form of mating Joint.

Fig. 2 is a sectional view of the slabs of Fig. 1 when Joined.

Fig. 3 is a sectional elevation showing another form of Joint.

Fig. 4 is a sectional elevation showing another form of joint.

Fig. 5 is a sectional elevation showing another form of Joint. I

Fig. 6 is a sectional elevation showing another form of joint.

Fig. '7 is a sectional elevation showing another form of Joint.

Fig. 8 is a sectional elevation showing another form of joint.

Fig. 9 is a sectional elevation showing another form of Joint.

Fig. 10 is a sectional elevation showing another form of joint.

Fig. 11 is a sectional elevation showing another form of joint.

Fig. 12 is a sectional elevation showing another form of'joint.

Fig. 13 is a sectional elevation showing another form of joint.

Fig. 14 is a sectional elevation showing another form of Joint.

Fig. 15 is a sectional elevation showing another form of joint.

Fig. 16 is a sectional elevation showing another form of joint.

Fig. 17 is a sectional view showing the slabs before interlocking, the interlock involving a deformable tongue.

Fig. 18 is a sectional view of the device of Fig. 17 assembled.

Fig. 19 is a sectional'view showing the slabs before interlocking, the interlock involving a deformable tongue.

- form'of'joint.

' Fig. is aise'ctional-view ofthefievice of Fig. 19 assembled- I Fig. 21 is a sectional view showing another Fig. 22 is a sectional view showing form of joint.

Fig. 23-is a sectional view showing form of joint.

Fig. 24 is a sectional view showing form of joint.

Fig. 25 is a sectional form of joint.

Fig. 26" is a sectional view showing form of joint.

Fig. 27. is a sectional view showing form of joint.

Fig. 28 is a sectional view of a slab showing a tongue as a separate element apart from the edge member.

Fig. 29 is a sectional view through a joint involving a spline.

Fig. 30 is an edge view of one of the slabs of Fig. 29. I

Fig. 31 is a composite plan view of two slabs using an interrupted tongue and groove.

Fig. 32 is an assembled plan view of two slabs using hook means for attaching the two slabs together.

Fig. 33 is a sectional view showing; the device of Fig. 32 assembled. I

Fig. 34 is a fragmentary perspective view of a button and slot arrangement for joining the two slabs.

F18. joint.

Fig.

another another another view showing another another another 35 is a sectional view of another form of 37 is a sectional view of another form of 38 is a sectional view of another form of 39 is a sectional view of another form of 40 is a sectional view of another form of Fig. 41 is a sectional view of a joint involving the use of grout or the like.

Fig. 42 is'a sectional view of another form of joint.

Fig. 43 is a sectional view of another form of joint.

Fig. 44 is a sectional view of another form of joint.

Fig. 45 is a sectional view of another form of joint.

Fig. 46 is a sectional view of a tongue and groove joint, in which the tongue is provided with an enlargement at its end.

Fig. 4'1 is a sectional view of a tongue and groove joint, in which the tongue is provided with an enlargement at its end.

Fig. 48 is a sectional view of a tongue and groove joint, in which the tongue is provided with an enlargement at its end.

Fig. 49 is a sectional view of a tongue and groove joint, in which the tongue is provided with an enlargement at its end.

Fig. 50 is a sectional view of a splined joint.

Fig. 51 is a sectional view of a splined joint.

Fig. 52 is a fragmentary perspective view of two slabs provided with means for locking the same together on the hinge principle.

Fig-53 is a sectional view of the device of Fig. 52 assembled. i

Fig. 54 is another form of joint.

36 is a sectional view of another form of Fig. 55 is another form .of joint.

Fig. 56 is a sectional view of a spline type joint. Fig. 5'7 is a sectional view of a spline typ doint. Fig. 58 is a sectional view of a spline type joint. Fig. 59 is another form of joint.

6 Fig. 60 is a sectional view of a joint involving the use of dowels or the like.

Fig. 61 is a sectional view of ajoint involving the use of grout or the like.

Fig. 62 is an edge view of one of the slabs of Fig. 61.

Fig. 63 is a view of a joint in-which the metal is not exposed on one face.

Fig. 64 is a view of a joint in which the metal is not exposed on one face.

Fig. 65 is another form of joint in which the metal is not exposed on one face.

Fig. 66 shows another form of joint.

Fig. 67 shows another form of joint.

Fig. 68 shows another form of joint.

Fig. 69 shows another form of joint.

Fig. 70 shows another form of joint.

Fig. 71 shows another form of joint. Fig. '72 is a sectional view of a joint using an attaching means not part of the slabs themselves.

Fig. '16 is a perspective view of the attaching clip of Fig. '75.

Fig. '17 is a sectional view of two slabs joined" together by means not integral with the slabs.

Fig. 78 shows a method "or hanging two slabs where that means also constitutes a joining means.

Fig. 79 is a perspective view of the hanging means of Fig. '78.

Fig. 80 is a perspectivepartly in section of a modified form of slab.

Fig. 81 is an enlarged sectional detail of the slab of Fig. 81.

Fig. 82 is a perspective partially in section of another form of slab showing its interior construction.

Fig. 83 is a perspective partially in section of another form of slab, and

Fig. 84 is a sectional view through the joint between two slabs constructed according to Fig. 83.

In the drawings, many figures show the metal element and slab outline as a single line for ease of illustration. It is to be understood therefore, that the parts fit closely together with no space therebetween, unlessotherwise indicated in the description.

In Fig. 1 the body of a slab A is shown at i of a suitable cementitious material of which gypsum is a type. This material may contain the usual fillers such as fibers, wood chips or the like. While gypsum has been found to be an advan-' tageous material because of its lightness, yet where greater strength is desired in the slab body itself and weight is of no consideration, this body may obviously be made of other materials such as concrete, magnesium oxychloride or sulphate ce-' ments or'the like. Inasmuch as one of the primary objects of the invention is to provide a substantially fireproof material, the body of such vided with a metal element designated generally at 2, this metal element embracing the edge of the body I and having its ends folded back upon itself to form a top flange 3 and a bottom flange l with a central vertical web 5. The flanges 3 and 4 in the folding over operation should preferably be provided with slight spaces 8 therebetween in order to accommodate the portions 1 of the corresponding flanges on the complementary edge member carried by the contiguous slab.

In order to prevent either during shipment. manipulation or otherwise, these edge members from pulling away from the bodyl of the slab, ears 8 are provided punched out of the material of the lower flanges 4 and in the pouring operation become embedded in the slab body. As a result it is not possible to accidentally displace these edge members from the slab.

When the two slabs are assembled on the job either as a wall, floor, ceiling, roof or the like, they assume the form shown in Fig. 2 in which each edge member so interlocks with the complementary or corresponding member on the adjacent slab that a substantial I beam construction results. It is to be noted from an inspection of Fig. 2 that a particularly sturdy construction occurs due to this joining interlock, not only by reason of the fact that an I beam is formed, but also byreason of the overlapping arrangement of the two metal members to form a triple thickness of flanges at the top and bottom joined by a double thickness vertical web.

As a result of this type of construction it will be apparent that the load sustaining value of a floor or roof deck formed therefrom is traceable directly back to the load sustaining value of the interlocking edge members rather than being dependent upon the strength of the body I. For this reason the ratio of supporting element spacing to slab thickness may be as great as 24:1 and greater, whereas in wood constructions this ratio is many times down as low as 12:1.

One of the advantages of the present construction resides in the fact that these units may be made in any lengths as long as the total weight of the unit is kept within the range where one or two men can handle them. It is contemplated that these sections 'will run from 12 to 16 inches in width, from 1 to 3 inches in thickness and from 6 to 15 feet in length. The load sustaining value of any unit will be dependent, of course, upon the gauge of metal used to form the edge members and the gauge used therein will in turn be dependent upon the necessary initial expense plus the cost of formation. For economical use I have found that cold ,rolled steel is admirably adapted for most constructional purposes.

In Fig. 3 the metal member attached to the slab A has its ends turned back upon itself to form a double thickness 9, the upper end or flange projecting beyond the edge of slab A and terminating in a V I0, which as shown flts into.a corresponding V H of the metal member attached to slab B. This latter element is provided with angular bends l2 embedded in the body I of the slab B to prevent the same from accidentally separating therefrom. The extreme end of the bottom flange 9 underlies'the bottom flange of the metal element on slab B as at l3. This type of construction involves the use of the I beam principle of Fig. 2. It will be apparent that as the slabs A and B are forced together, the metal element on the former snaps into engagement with the latter and serves as a positive interlock.

-In the previously described forms of the inv be found desirable though this may ventlon as well as those hereinafter described, the invention contemplates the use when necessary of means to prevent accidental displacement of the metal member for the slab body. This means may take the form of cars I, angular bends I2, or an expanded or perforated portion or the like.

Fig. 4 shows a type of Joint in which the metal member on the slab A has a top flange constituting a double thickness due to the material being reversed upon itself and also being provided with a right angular bend H to prevent undue separation of the metal from the slab. The end I ha of the top flange 5 is slightly modified from the showing of Fig. 3 but likewise seats in a corresponding groove Ila of the metal element on slab B. The lower flanged portion of the metal element on slab B is of double thickness, shown at l5, which is receivable into a groove l6 formed by a doubling back upon itself of the lower portion of the metal of the element attached to slab A so as to secure an interlock at this point. A tip I! may be turned up on the metal element of slab A to become embedded in the material and prevent separation ofithe parts. As shown, not only is there a snap interlock between the two metal elements at the top in much the same manner as Fig. 3, but there is a definite interlock at the bottom in the same manner as Fig. 2. This makes I for a sturdy construction.

Fig. 5 shows a construction in which the top portion is very similar to that of Fig. 3 except that the spring portion I8 is in the form of a surface of revolution which flts into a corresponding groove or recess ID in the metal element attached to the slab B. In many instances it will be found unnecessary to interlock the two metal elements at the bottom at all and for this reason no interlock has been shown at the bottom of this form of Joint.

In Fig. 6 the metal element attached to slab A is shown to be provided with a double thickness flange 20, the end of which is deformed into a surface of revolution 2| with a projecting end 22 at an angle thereto. The deformed portion 2| likewise flts a corresponding groove 23 in the element attached to slab B so as to form a spring flt therewith. The angular end 22 serves to additionally strengthen the flange 20. In the case of either or both of the metal elements it may to turn up the extreme ends the same in the body of the separation of these parts, albe omitted where desired.

In Fig. 7 a form of tongue is shown to consist of the metal of the element attached to slab B folded back upon itself at the bottom and brought up alongside of the web and then deformed into a spring tongue 24. The element attached to slab A is provided with a groove 25 of substantially V shape. It is contemplated that the tongue 24 shall be opened normally and before assembly, to a point where it will not quite fit within the groove 25. When the two slabs are then forced together, this spring tongue 24 is caused to slightly collapse, which thereby increases the friction between the metal surrounding the groove 25 and insures a positive interlock between the parts.

In Fig. 8 the edge of the slab A is slightly lessened in thickness and completely covered by the metal element 25 which forms in effect a tongue in itself. The element attached to slab B is doubled back upon itself at the top and bottom to form double thicknesses of metal at 21, and these portions overlie and frictionally engage the as at l2 to embed slabs to prevent metal element attached to slab A to form a rigid and tight interlock.

Fig. 9 shows a form somewhat similar to that of Fig. 8 except that the tongue 28 on the slab A is of a thickness less than the complete thickness of the slab. This therefore serves to provide a shiplap joint between the parts, which is of advantage.

Fig. 10 shows a simple shiplap arrangement where both the edges of slab A and slab B are entirely protected by complementary elements 29 and 30. The ends of these elements may be turned at an angle as at l2, in order to embed vthem in the body of the slabs and prevent accidental withdrawal. While there is no definite interlock between these two parts as shown, yet' it is a simple matter to drive a nail 3| through the overlapping ends of the two slabs. The invention contemplates, of course, that the metal on the edge of any slab shall be of a gauge which will permit the driving of a nail therethrough. While ordinarily a nail will not hold in neat gypsum and only imperfectly in a gypsum body having an admixture of wood chips or the like, yet when the nail is driven through metal and into the gypsum, it is practically impossible to remove the same due to the fact that the metal through which the nail passes grips the nail as well as the gypsum body. The fact that the nail passes through the metal prevents any loosening of the former in the gypsum body, which would otherwise take place.

In Fig. 11 the slab A is provided with a shiplap in which the projection 32 is protected with a metal element in the form of a wedge adapted to frictionally engage a corresponding groove in the slab B. This makes for a tight joint.

In Fig. 12 slab A is provided with an ovoid projection 33 protected and covered with a metal element 34 which engages a similarly covered groove in the slab B. In view of the fact that the projection 33 is ovoid in character, such a construction will bear a distinct load without any separation of the two slabs. This is due because the surfaces in contact at the points C are substantially at right angles with the applied load. If the tongue and groove were surfaces of revolution, these surfaces would be more nearly angular and hence there would be a definite tendency for slippage of the parts, but. as shown, this tendency is overcome.

In Fig. 13 a stepped tongue is shown engaging a corresponding groove, both of which are protected and covered by metal elements.

Fig. 14 shows a joint in which two distinct tongues 35 and 36 in the slab A engage corresponding grooves in the slab B. It is contemplated, of course, that in the form of joint shown in this and the preceding figure, there may be a tight frictional joint between the tongues and the grooves in order to form a true interlock and prevent undue separation of the slabs when assembled.

Fig. 15 illustrates a joint formed with a single tongue 31 in the slab A entering a corresponding groove in the slab B.

In Fig. 16, which is somewhat similarto the showing of Fig. 15, the tongue 38 is provided with a rounded end 39. This makes for ease of as sembly as it is only necessary to get this tongue started in the groove and thereafter any irregularities will straighten themselves out as the two slabs are pushed together.

In Fig. 17 the slab A is provided with a metal element having a deformable tongue 40. This tongue is preferably formed of metal turned back upon itself, although there may be some separation of these thicknesses where desirable. The slab B is provided with a metal element having a curved or angular groove 4| so that when the parts are forced together as in Fig, 18, the tongue 40 will become deformed in entering the groove 4| and it will be extremely diflicult to separate the two slabs after assembly. This forms a very positive interlock and even though the tongue becomes slightly warped or displaced during shipment or handling, yet it is contemplated that it will be of suflicient lightness to permit the same to engage the mouth of the groove 4| and then upon exerting force the two slabs may be shoved close together with consequent deformation of the tongue 40 as shown.

In Fig. 19 the slab A is provided with two deformable tongues 42 and in this case they are receivable in the metal element of the slab B in diverging grooves 43. This, as in the case of Fig. 18, causes a deforming or separation of the tongues 42 when the parts are assembled as shown in Fig, 20.

In Fig. 21 the slab A is provided with a pair of metal covered tongues 44 receivable into corresponding grooves in the metal element of slab B. These tongues should obviously be sharply wedge shaped and fit tightly into the corresponding grooves. As a matter .01 fact, it is preferable that there be-some slight dissimilarity between the tongues and the-grooves in order to increase the frictional contact between the parts.

In-Fig. 22 another V type of tongue and groove is shown in which the base of the tongue 45 is substantially the thickness of the slab A. Asin the case of Fig. 21 this tongue fits tightly into a corresponding groove 46 in the slab B.

Fig. 23 shows a slightly modified form of joint in which wedge shaped tongues 41 on the slab A engage corresponding grooves in the metal element of slab B and the latter is provided with a square tongue 48 engaging a corresponding groove in the. slab A. As a result, not only is there a wedging and highly frictional contact secured between the two slabs, but due to the fact that there is a definite horizontal engagement between the metal'jparts, this form of slab is a very effective load sustaining section and any tendency of slippage or separation of the slabs is avoided.

Fig. 24 shows a joint in which the slab A has its edge portion provided with a metal element defining a 45 angular tongue 49 which fits-a corresponding groove in the element attached to slab B.

Fig. 25 shows a slab Aprovided with -a greatly elongated tongue 50, the bottom of which is substantially parallel with thetop or bottom face of the slab and is receivable into a corresponding groove in slab B. This type is particularly effective in that not only. may a tight wedge, highly frictional joint be secured, but due to the horizontal surfaces in contact, no slippage of the parts will occur under load.

Fig. 26 is somewhat similar to the showing of Fig. 11, except that the tongue 32 in the slab A has been reversed and it has been moved to a point nearer to the center of the slab so as to provide a vertical web as at SI and 52 in the metal member attached to slab B. This makes for greater strength. 1

In Fig. 27 the slab A is shown as being provided with a tongue 53 formed by turning the metal directly back-upon itself. It is received within a corresponding groove in the metal element attached to slab B. Such a construction insures a tight frictional joint which is accentuated if during the course of shipment or delivery the tongue 53 has become slightly bent or deformed. As the slabs A and B are shoved together, these irregularitiesnaturally straighten themselves out, but they cause the two slabs to bind in a particularly tight joint. In this figure a strengthening mesh 54 is shown in each slab which may be resorted to where a width of slab is desired requiring reinforcement. As a matter of fact, in any of the preceding or succeeding slabs, mesh may be used where found desirable. This mesh may be put in place during or after the casting operation and upon solidification of the plastic material of which the body s made, will be held in the proper position in the slab.

Fig. 28 shows an alternative method of providing a metal element with a tongue. In this case the tongue 55 need not be continuous but may project at intervals fromthe face of the element 55, the tongue 56 projecting through an opening 51 in the face of the metal element 55. As shown, it is preferable to provide the end of the tongue 51 with a perforated or expanded portion 58 to permit the plastic material to flow therethrough and cause the same to be tightly embedded in the body of the slab A. This form of tongue may then be used with the type of groove shown in slab B. see Fig. 27.

In Fig. 29 it may be desirable to provide each slab with a grooved metal element such as that shown for slab B in Fig. 27. This construction does not necessitate the use of two sets of dies. one to form a tongue and one to form a groove, but on the contrary both elements are provided with grooves and hence they can be made on the same dies. These elements are shown at 59 having grooves 80. The tongue which joins the two slabs together is formed of a sheet of metal or the like folded upon itself for strength, and wedged between the two grooves at the time of erection. This tongue is shown at 5|.

Fig. 30 being an edge view of one of the slabs of Fig. 29, shows the groove 69 running the continuous length of the slab and prior to the insertion of the tongue 6|.

In some instances it may be desirable to have the tongue on one slab instead of running continuously the entire edge thereof, being of interrupted character as shown in Fig. 31. In this instance a series of tongues or fins 52 are adapted to engage corresponding grooves or sockets 53.

Where a definite and positive interlock between two slabs is desired, and it is not thought sufficient to depend upon friction alone, the form shown in Fig. 32 may be resorted to. In this case the element attached to slab A is provided with a hook 63 adapted to penetrate the member attached to slab B through the aperture 64. By longitudinally sliding the slab A on the slab B after the above operation, the nose 55 of the hook engages the metal of the slab B at the point 68 and positively prevents withdrawal of the two slabs from each other. Fig. 33 is a sectional view showing this construction with the parts interlocked together.

Fig. 34 shows a form of positive interlock somewhat different from that of Figs. 32 and 33. In the present instance the slab A is modified with a metal member 69 having buttons projecting therefrom with enlarged heads 70 adaptedto be insertable through an enlarged portion ll of a corresponding slot in the metal element I2 of slab B, whereupon by longitudinally sliding the slab A on the slab B the shank 13 of the button on slab A is made to enter the restricted portion 14 of the slot in the slab B, with consequent positive interlocking of the parts.

In Fig. 35 a tongued and grooved joint is shown. The slab A is provided with a greatly elongated tongue 61 which extends at an angle to the horizontal center line of the slabs. It engages in a tight frictional joint a corresponding groove in the slab B. In this way when load is placed upon slab A, there is a tendency toward tighter engagement between the two slabs and no tendency whatever for the two to separate. This is of advantage.

Fig. 36 shows a slightly modified form of tongue 68 which is curved into a corresponding groove in the slab B. As in the case of the form of Fig. 35, the slabs may be placed in either position, that is, with the nose or tongue pointed either up or down, dependent upon the circumstances and the direction in which the load is to be borne. In the case of Fig. 36 the tongue 58 may be of a slightly deformable material to have the same eifect as the combination shown in Fig. 18 when the two parts are assembled.

Fig. 37 shows a form of interlock between slabs in which one slab is simply laid upon the other to prevent lateral displacement. This in many instances will be found sufiicient, particularly where each slab is definitely tied to its support or retaining member. In the present instance the slabs are of the shiplap variety but of such a nature as to prevent lateral separation.

Fig. 38 also shows a joint on this principle, in

which, however, a downwardly projecting tongue 15 is provided in the metal element of slab A which engages a corresponding groove in the element attached to slab B. This gives not only the desired lateral interlock but due to the frictional engagement between the tongue and groove it will be found extremely difficult to. cause relative.

movement between the two slabs in a vertical direction.

Figs. 39 and 40 are self-explanatory and show modified forms of shiplap, as in the case of Fig. 37.

In Fig. 41 the metal element attached to slab B is provided with an upwardly projecting end 16 receivable into a corresponding groove 11 on one face of slab A. This very definitely prevents any lateral movement between the two slabs. It is contemplated that a plastic mix of gypsum, cement, metal, .plastic paint, artificial resins or any material which may be made to flow will be inserted in the space between slabs and which upon solidification will occupy the position shown at 18. This material will then prevent any vertical movement between slabs which might otherwise take place.

Fig. 42 shows a modified form of shiplap to prevent lateral movement between the slabs and is self-explanatory.

Figs. 43 and 44 show'shiplaps involving surfaces of revolution, which makes necessary the rocking of slab A containing the tongue or projection into slab B which contains the corresponding groove or depression, but after once in place, both lateral and vertical movement between the slabs is prevented.

Fig. 45 shows a construction arranged to form an interlock on somewhat the same principles as in Figs. 43 and 44, but in addition a deformable tongue 19 is provided in the metal element attached to slab'A which engages a corresponding roove in the metal element attached to slab B. Figs. 46, 47, 48 and 49 show various forms of dovetall interlocks where the projection in one slab is provided with an enlargement at the end, making necessary the longitudinal sliding of one slab into another. In many instances this positive form of interlock will be found to be desirable. In this type of joint it may be desirable to provide the neck 88 of the projection in one slab as an opening sumcient to permit the plastic material of which the body is made, to flow therebetween and fill the hollow enlargement. This construction is shown in Fig. 49 in contradistinction to the showing in Figs. 46, 47' and 48, in which no opening remains in the neck, but on the contrary the stiffness of the metal of which the enlargement of the tongue is made is relied upon to prevent separation of the parts.-

Fig. .58 shows the slabs A and B provided with similar grooves arranged longitudinally of an edge and adapted to receive a spline 8i having enlarged ends 88. This spline is to be driven in place after the slabs are placed contiguousto each other.

Fig 51 shows a modified form of splined joint, which is self-explanatory.

In Fig. 52 the slabs A and Bare each provided with metal elements having interrupted tongues and grooves formed on the principle of a hinge. That is, each element is adapted to be split laterally as at 88, and thereafter the parts 88 pushed inwardly to form a surface of revolution and the parts pushed outwardly to form a complementary surface of revolution. When the slabs A and B are thereupon placed together and a rod 88 inserted as shown in Fig. 58, the two slabs will be.tied permanently together. Obviously by suitably shaping the parts 88 and 88, a square or other shape rod or tie means may be used with the same effectiveness.

-xIn Fig. 54 the slabs A and Bare shown to be provided with metal edge members having a longitudinal groovetherein as at 81, which is substantially a surface of revolution and adapted to receive a rod 88 therebetween. This construction while not tying the two slabs together laterally, does serve to prevent any relatively vertical movement between the two. Where either slab A or B is positively tied to a support or carrying member: such as shown in Fig. 68, the presence of the rod 88 positively prevents any upward movement of the slab not tied to the support.

Fig. 55 shows the slabs A and B tied together as by an ordinary dovetail 88. Presence, however, of the metal edge member on each of the slabs serves to very materially strengthen the dovetail for its effectiveness would be entirely lost without such strengthening members. In such a construction, of course, the two, slabs A and B must be slid longitudinally on each other in order that the dovetail may engage its conresponding groove.

The construction shown in Fig. 56 is one in which both slabs A and B are providedwith longitudinal grooves formed by bending the metal of the edge members directly upon itself to form grooves 88 of substantially the thickness of the metal of the edge members themselves. These grooves are then adapted to receive the single thickness of sheet metal 8| as a tongue or spline. This tongue or spline 8| may be continuous and extend the entire length of the grooves 88, or it may be interrupted and take the form of short pieces. In the latter case, these, tongueslmay be effectively formed from scrap material. Due

to the fact that the metal is comparatively thin,

any deformation thereof from a plane surface greases Y tends to cause a more efllcient bond and interlock between the two slabs.

As a modification of the splineshown in Fig. 88, that disclosed in Fig. 57 is referred to. In that case the slabs A and B each are provided with grooves 88 constructed substantially as described in Fig. 56. The spline or tongue 82,how-

ever. instead of being of a continuous double" bent back spring ends 88 opened up to a thickness or width greater than the mouth of the vent separation of the slabs. Such a construction forms a very tight interlock.

A double tapered spline 88 is shown in Fig. 58 as binding the slabs A and B together, the tapered ends of the spline engaging corresponding grooves 88 in the two slabs. As in the case of Fig. 58, the spline may be continuous or it may be interrupted as desired. The spline 88 may likew'se be made of wood or any material which will give the desired interlocking effect with high friction.

Another construction which may be satisfactory to tie the slabs A and B together and to prevent relatively vertical movement between the two is shown in Fig. 59 to consist of a sphere 81 receivable into complementary sockets 88 and 88 in the slabs A and B respectively. These sockets may conform closely to the sphere 8,1 or may be of such dimensions as to cause the sphere to be wedged thereinto and even deformed when the two slabs are closely pressed together. If the sockets are to closely fit the sphere, the latter may be formed of wood, metal 'or any non-compressible material and even gypsum or concrete, but where a compression flt is desired, some such material as rubber may be used for the construction of the sphere.

Dowels may be used to tie the two slabs A and B together in some such manner as shown in Fig. 88, where individual dowels I88 having tapered ends are receivable in a tight friction manner in corresponding sockets in the metal members 'anvinspection of Figs. 61 and 62.

-{One of the diillculties enwlmtered in a fireproofconstruction involving the use of metal, is

- in protecting the same from theravages thereof.

While any of the slabs heretofore described may be protected as by the use of plaster or other fireproof material applied over the metal, yet in some instances'itwill be found desirable to conis provided with a metal member having a groove.

I88 to receive a correspondingly tapered tongue I88 onthe metal member carried by slab B. It is thickness as shown in Fig. 29, is provided with 1 to be noted that both slabs A and B have a substantialbody of set cementitious material I04 protecting the metal elements, that is, instead of the metal member having a portion overlying one of the faces of the slabs, as for instance in Fig. 53, the metal is actually embedded in the slab body. While in Fig. 63 the metal ends are shown bent angularly as at I2 to prevent accidental loosening or withdrawal of the metal members from the slabs, yet obviously the tongues I as shown in Figs. 1 and 2 may be used or the metal itself'may be expanded or perforated as at II in Fig. 28' to serve the same purpose.

A slightly more emcient form of fireproofing is shown in Fig. 64 in which each slab is provided with a portion I OI completely underlying or overlying as the case may be, the metal element on its contiguous neighbor. This causes a staggered joint arrangement between the set cementitious material between the two slabs and metal elements of such slabs and such construction serves. to assist in preventing the passage of heat to the metal member.

In some instances it will not be found necessary to form fireproof material on each side of the metal members, but on the contrary but a single underlying or protecting portion may be used. In Fig. 65 the slab B is shown to have an underlying portion I06 slightly out of line with the joint between the metal members on the two slabs. Obviously this protecting portion I08 may be on either slab and may be underneath or on top of the metal members, as circumstances will dictate.

Fire tests on slabs having joints substantially as indicated in the Figs. 63,64 and 65 show that there is a tendency for an undue rise in temperature of the metal and the slab directly above the joint when the under side is subjected to extreme heat. This is probably due to the fact that under the action of heat the gypsum expands and opens the joint at the point where there is no metal, with the result that the metal directly above that opening is subjected to the action of either the fire or the heated gases from the fire. This detrimental effect may be avoided to a great extent by extending the heel portion on one slab to a point where the Joint will actually clear the metal.

A more satisfactory form of construction, however, is shown in Fig. 66, in which the slab A is provided with a material thickness of gypsum I01 directly beneath the bottom flange of the metal element in that slab. The slab B is provided with a lip or toe I08 underlying the part III! to form a shiplap joint at this point. Such a construction it will be seen, even if this joint opens up under the action of heat, will to-a great measure prevent the flame or heated gases from impinging upon the metal, as they will be directed against the bottom of the body of gypsum I01. Such a construction may be formed by either using a full sized metal section and increasing the thickness of the slab, or by decreasing the depth of the metal element and using a normal thickness of slab.

In Fig. 67 a modified form of joint is shown in which the lower portion of the metal element attached to slab A is provided with a shorter lower vertical web portion I09 which carries lower flange IIO of this section higher up in the slab A than the corresponding flange 'in slab B. This type of Joint still permits a portion of gypsum I I I to be located below the flange I I0 and gives maximum depth to the toe I I2 in the slab B.

In Fig. 68 the metal element attached to slab A is slightly modified from the showing in Fig. 67 by eliminating the vertical web I09 of the former figure entirely and in its place extending an expanded or perforated portion III of the member attached to slab A into the body of the slab.

This type of metal Joint is likewise shown in Fig. 69, with the addition of a horizontal fire stop or barrier I. Such a construction will effectively prevent passage of heat through the crack between the slabs in case it should open up, for the heat in order to reach the metal at all must turn several corners and be deflected downwardly.

In Fig. 70 the type of Joint shown in Fig. 69 is again illustrated but using in this instance a vertical fire stop or barrier II I for the same purpose. Obviously the type of joint shown in Fig. 69 may be used with the fire stop II! or the fire stopi I 4 ilnay be used with the type of Joint shown in Fig.

In some instances it may be found desirable to eliminate the lower flange of one of the metal elements entirely and such a construction is shown in Fig. 71 which for example eliminates the lower flange on the metal element attached to slab A. In order to compensate for this loss of stiffness and strength which the flange would otherwise lend to the slab, there may be inserted a reinforcing rod, bar or the like II6. In some instances, however, it will be found unnecessary to use such a reinforcing element.

In the previous modifications described, the metal members have taken the form of substantial I beam constructions in which but a single web is provided. It will frequently happen, however, that a construction will be desired where more than a single vertical web is required to lend extreme strength to the units. Such a construction is shown in Fig. 72, where each slab A and B is provided with a substantially rectangular metal member which involves a vertical web III and an additional vertical web H8. The latter is perforated or expanded as at II9 to permit cementitious material of which the body A is made, to pass therethrough and effectively tie the metal member to the slab itself without the use of extraneous tie members. It is to be noted in the construction shown in Fig. 72 that there is no positive connection between the slabs A and B. This tie or interlock may be effectively taken care of as by means of the tie I at either the top or bottom or both thereof, having angularly pointed ends I2I forced down into the cementitious material of which the slabs are made. These ends I2I closely fitting the overall width of two adjacent metal members, causes the two slabs to beforced tightly together and held in that position against accidental displacement. As in previously described modifications, a mesh or strengthening member I22 may be used to give additional strength to the unit.

An effective method of tying a slab construction as shown in Fig. 72 to a supporting member, is shown in Fig. 73 to consist of a clip or plate I23 nailed as at I24 to one of the slabs, and having a slot I25 conforming closely to one of the flanges of the I beam or channel I26. Such a combination of parts effectively prevents longitudinal and vertical movement of the slab, and its neighbor being tied closely to it, both slabs are prevented from becoming accidentally displaced. Obviously such a construction may be used not only with the type of slab shown in Fig. 73, but with any of the preceding slabs. A detail of the plate or clip I23 is shown in Fig. 74.

Where it is desired to hang a 'slab from an overhead support, the plate may take the form as shown at I21 in Figs. '75 and '76. In this case the plate is provided witha deformed portion I28 conforming closely to the tongue and groove and secured therebetween, an upwardly projecting portion of the plate being provided with perforations I28 adapted to be engaged by a hanger I3ll secured to a furring or beam I3I which serves as an overhead support. In order to positively secure the plate I21 to either of the slabs, nails I32 or the like may be used. Obviously in some instances the nails I32 will be found sjufllcient, particularlywhere slabs with-, out interlocking projections or tongues are used.

A slightly modified form of interlock using the slabs of Fig. '73 is shown in Fig. 77, consisting of a double angular clip- I33 having pointed and angular ends I34 embedded in the material of the slabs A and 13.

Another method of hanging slabs of this type from'an overhead support is shown in Figs. 78 and '79 to consist of a hanger having a doubled vertical portion I35 with supporting arms I36, the ends of which are embedded in the slabs as at I31. This clip may engage a hanger element I33 which in turn engages a supporting mem- -ber, as shown in Fig. '75.

Where it is desired to construct a slab in which the edge portion containing the metal element is of greater thickness than the main body of the slab, a construction as shown in Fig. 80 may be resorted to. Here a slab A contains a metal element I39 on at least one edge thereof and preferably opposite edges having an angular projection or lip I40 extending inwardly of the slab and upwardly as at Hi to be embedded in the body I42. Due to the fact that a space exists between the portion MI and the downwardly extending end I43 of the metal element, the plastic material of which the slab A is made may fiow thereinto and completely fill the body of the metal member I39. Where a mesh or strengthening reinforcement I44 is used, such a construction will be found to be of material advantage in properly spacing the mesh in the body of the slab. In constructing such a slab, the metal element I39 is put in place in the mold, the mesh I44 inserted between the parts MI and I43, as shown in Figs. 80 and 81, and then the plastic material molded therearound and into the interior of the part I39. As shown, the main body I42 is of less thickness than themetal edges thereof, which will be found to be of advantage in many cases.

Fig. 82 shows a complete detail of the interior construction of the slab using the metal-elements of the type shown in Fig. 78, in which the inner wall H8 is perforated as at III! to permit the plastic material to flow through the inner web portion of the metal member and consequent bonding of the metal member with the slab body. It will be found to be of advantage in some instances to provide a shiplap end as at I45 on such slabs. This shiplap may be either at the lateral ends or longitudinal sides of the slabs as desired, and the overlapping portions may be nailed together in some such manner as shown in Fig. 10.

A modified form of metal edge member which may attain maximum strength is shown in Fig. 83 to consist of metal elements suchas a pipe or the like I46. These pipes may be perforated as at I46a to permit the cementitious material interior thereof and bond the parts together. Where it is desired to interlock two of these slabs, a double-headed spline I41 may be used as shown in Fig. 84. The space between metal elements I46 in contiguous slabs may be filled with grout or the like I48.

Where a slab of the type shown in Fig. 22 or 23 is used, that is, where one slab is provided with a metal element having a projection which fits into a corresponding groove or socket in its contiguous neighbor, the mesh may be readily spaced in the proper location of the slab body by inserting one edge thereof into the interior of the projection at one edge' and on top of the metal forming the groove on the opposite edge of the slab. These surfaces form a definite support for the mesh during the pouring operation and serve to very definitely space the mesh to the proper position within the slab body.

Of course, it is to be understood in such a construction as shown in Figs. 63 to 71 inclusive for instance, any type of interlock may be used as shown in any of the other figures. In the same manner the slabs of the type shown in Figs. 72 and 73 may likewise be provided with an integral interlock or not, as circumstances will dictate.

The metal members herein shown and described may be used on either one edge of a slab,

on opposite edges, or on all four edges, as may be determined by the particular circumstances in hand. Where such metal members are used on all four edges, they may be joined to their neighbor in the same slab or not. Such joining means may be made by either pins, interlocks, shiplap joints, soldered, riveted, or secured together in any known manner.

In slabs having non-uniform top and bottom surfaces, such as shown in Fig. 3 for instance, or slabs not entirely symmetrical in lateral crosssection, as for instance in Fig. 17 or 25, in some cases it will be found desirable to invert the slab from the position shown in these figures and, of course, the invention contemplates such other position.

Obviously the slabs of this invention may be used as sustaining walls,partition walls, roof decks, floors, ceilings and in any position vertical, horizontal or any angle therebetween, and tied to, laid upon or hung from any desirable type of support. It will be obvious from the foregoing description that by making the metal element of suitable gauge, these slabs may be sawed in any desired lengths to fit the particular circumstances of erection, and applied in exactly the same manner as wood lumber. It is contemplated that due to the extreme lengths in which this material may be made by reason of the fact that the load sustaining portion thereof is the metal element, one slab may span any distance up to its length without regard to support spacing or the occurrence of joints, that is, a joint need not necessarily occur directly over, under or coincide with the support to which the slab is attached or upon which it rests. It is preferable, of course, in a building construction that the joints between contiguous rows of units be staggered in order to give maximum strength.

While in certain of the modifications shown, two contiguous slabs are adapted to be interlocked as by relative longitudinal movement, such for instance those of the dovetail interlocking type, obviously this dovetail and its modifications may be constructed and arranged for engagement with a corresponding socket or slot in mentitious material between said elements and a slab face.

2. A precast slab 01' set plastic material having on one edge thereof a metallic load sustaining 'element, said element having a plurality of interlocking means for cooperation with complementary portions of an adjacent slab in which the interlocking means include a plurality of tongues adapted for interlocking engagement with a plurality of complementary grooves in an adjacent slab.

3. A precast slab of set plastic material having on one edge thereof a metallic load sustaining element, said element having a plurality of interlocking means for cooperation with complementary portions of an adjacent slab in which the interlocking means include a plurality of tongues having head portions of greater width than their intermediate neck portions for interlocking engagement with a plurality of complementary grooves in an adjacent slab to form a joint therewith.

4. A precast slab 01' set plastic material having on one edge thereof a metallic load sustaining element, said element having a plurality of interlocking means for cooperation with complementary portions of an adjacent slab in which the interlocking means comprises a plurality of aligned tongues, each tongue including a web portion spaced from the slab body, the total length of said aligned tongues being less than that of the metallic element on which they are mounted, whereby a locking element may be passed behind said web portions to form therewith an interlock with an adjacent slab.

5. A building construction including a plurality of adjacent slabs of set plastic material, each of the slabs having on an adjacent face a metallic load sustaining element having a plurality of spaced, aligned tongues each including a web portion spaced therefrom, the-tongues of one slab lying between the adjacent tongues of the other slab, and a locking element passed behind the web portions of all the tongues to form therewith a hinge joint.

6. A precast slab of set plastic material having on-at least two opposite edges thereof complementarily tongued and grooved metallic lqad sustaining element of less height than the thickness of the slab, each of said load sustaining elements including a web portion lying in the plane of the slab edge and one or more flange portions spaced from the slab faces by a substantial thickness of fireproof material.

7. A building construction including a plurality of precast, slabs of set plastic material having on adjacent edges thereof abutting tongued and grooved metallic load sustaining elements of less height than the thickness of the slabs, each of said loadsustaining elements including a web portion lying in the plane of the slab edges and one or more flange portions embedded in the slab material and spaced from both faces thereof by a substantial thickness of fireproof material thereby to form a fireproof I-beam construction.

8. A building slab having opposite faces at one edge beveled, and also having a groove in said one edge providing with said beveled surfaces a pair of projections, said slab at the edge thereof opposite the first named edge being provided adjacent one face thereof with a groove, and a tongue for wedging engagement with the projections on the adjacent edge of a second similar slab for joining the meeting edges of the slabs, said tongues and groves being plane surfaces, and located in vertical edges of the slab, and a vertical plane area between a tongue and a slab face at each of said edges.

9. A precast slab of set cementitious material having metallic members at opposite edges there of, one of said members constituting a groove and the other constituting a mating tongue, one of said members having a turned in end substantially at right angles to the slab face and embedded in the slab body but within the plane top and bottom of said slab. l

l0. A precast slab of set cementitious material having on at least two opposite edges complementary metal members each adapted to interlock with corresponding complementary parts on the edge of a slab erected adjacent thereto, said metal members having their end portions turned back and embedded in the set cementitious material of the slab.

11. Precast building units of set cementitious material having embedded in at least two opposite edges a bent joint member, a plurality of aligned spaced sheet metal loops at the front of said member and projecting from the face of the edge of the unit, the loops in one member staggered in relation to the loops on the adjacent member, each member also having at the back aligned spaced sheet metal braces and a coupling rod passed through the projecting loops of the meeting ends of adjacent units.

12. A building construction including a plurality of building units arranged with their longitudinal edges adjacent, the edge on one unit being constituted by a metallic web having a tongue frictionally engaging a corresponding groove in a metallic web on the adjacent unit, a flange at the bottom of each web at right angles thereto, each flange terminating in a stiffening end portion turned at-an angle to the flange, whereby the mated edges constitute an I-beam stiffened at the ends of its bottom flange.

CLARKE F. DAVIS. 

